| Window assemblies are an important part of buildings and have the function of transmitting the sun’s rays.Smart windows have the functions of regulating solar radiation and reducing air conditioning energy consumption,which has attracted the attention of researchers.Polymer stabilized cholesteric liquid crystal(PSCLC)composite materials,because of their excellent optical properties in the field of electrical response light scattering and reflection technology have certain practical applications,such as privacy protective glass,solar heat dissipation and color switching curtain wall,etc.,the research of PSCLC dimming devices has made great research progress.In buildings,visible light in sunlight can provide indoor lighting,while infrared light,which carries a lot of heat,can provide heat indoors,and the two work together to provide users with a visual and temperature environment in the building.Therefore,compared with ordinary glass windows,dual-function dimming devices that can control visible and infrared light can better meet the important needs of building users for comfortable life.However,at present,the dimming band of PSCLC dimming devices is single,and can only adjust visible light or infrared light,with a single function.Therefore,it is of far-reaching significance to provide comfortable life and promote the green development of buildings by studying how to enrich the functionality of devices and realize PSCLC intelligent dimming film that is independently and dynamically regulated in the dual spectrum of visible light and infrared light.In this paper,an interdigital electrode is introduced to change the electric field distribution in the device by starting from the electric field response characteristics of Cholesteric liquid crystal(CLC)and polymer networks in polymer-stabilized cholesteric liquid crystal composites.Moreover,by adjusting the three key process preparation parameters related to the optical modulation range of the PSCLC dimming device in the dual band: interdigital electrode size,monomer mass fraction and liquid crystal box thickness,the dimming performance of PSCLC was further adjusted,and finally the PSCLC dual-function dimming device was successfully prepared.The dual-function PSCLC has an initial transmittance of 94% in the visible band and an initial bandwidth of 158 nm in the infrared band.The specific research content is as follows:(1)The influence of interdigital electrode size on the response characteristics of polymer network and CLC in PSCLC and dimming characteristics in the dual band.The modulation effect of optical performance of PSCLC devices prepared with interdigital electrodes of different sizes in the dual band and its influence on the driving voltage of PSCLC were studied.Studies have shown that the electric field distribution formed by the narrow width(25 μm)electrode gap is more conducive to the electric field response of liquid crystal and polymer networks.The PSCLC device prepared based on the interdigital electrode substrate with an electrode gap width of25μm and an electrode width of 115μm has the best optical performance,and its transmittance in the visible light band can be adjusted in the range of 94%～10.8%,and the reflection bandwidth in the infrared light band can be adjusted in the range of158nm～478nm.Therefore,the independent dynamic regulation of PSCLC in the dual band is realized,which enriches the functions of PSCLC.(2)The influence of monomer mass fraction on PSCLC polymer and its dimming characteristics in the dual band.The results show that the mass fraction of the monomer determines the density of the structure and morphology of the polymer network,and further determines the anchoring force of the polymer network on the liquid crystal molecule.The polymer network structure formed by low mass fraction(2.0wt.%)monomer is relatively loose,and the transmittance of PSCLC in the visible light band can be adjusted in the range of 94%～9.50%,and the reflection bandwidth in the infrared light band can only be adjusted in the range of 158nm～271.58 nm.Moreover,the dimming device is not easy to return to the initial state after the power is disconnected;The polymer network structure formed by the mass fraction(4.0wt.%)monomer is very dense,the transmittance of PSCLC in the visible light band can only be adjusted in the range of 94%～14.17%,and the reflection bandwidth in the infrared light band can be adjusted in the range of 158nm～674.28 nm.However,at this time,the operating voltage of the PSCLC is too high,which brings serious safety problems.(3)The influence of device thickness on the dimming characteristics of PSCLC in the dual band.The results show that when the device thickness is 10μm,the transmittance of PSCLC in the visible light band can be adjusted in the range of94%～22.94%,and the reflection bandwidth in the infrared light band can only be adjusted in the range of 158nm～481.05 nm.When the device thickness is 50μm,the transmittance of PSCLC in the visible light band can be adjusted in the range of94%～18.23%,and the reflection bandwidth in the infrared light band can only be adjusted in the range of 158nm～409.72 nm.When the device thickness exceeds 30μm,more CLCs are driven by vertical electric fields to be oriented and deflected rather than stretched and compressed by the polymer network,and the PSCLC tunable reflection bandwidth is narrower. |
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